As the global energy crisis and environment pollution become more and more serious, a new solution must be adopted in the development of the automobile industry. Electric vehicles are gradually attracting public attention due to its advantage of higher voltage, higher specific energy, better cycling performance and pollution free feature. Further, electric vehicles considered as the most promising automotive vehicles.
However, the lithium ion batteries of an electric vehicle need to operate in a certain temperature range to perform in its optimal state. Operating out of the certain temperature range affects the performance of battery and shortens the battery life. Operating at a higher temperature will reduces the battery safety level, and may further lead to gas releasing, smoking and liquid leaking. More seriously, it may lead to fire or unwanted combustion. Therefore, the temperature control of the lithium ion battery is critical.
The power battery generates a lot of heat during charging and discharging. If the heat cannot be removed in time, the battery temperature will rise significantly. Especially for large storage battery packs, since in order to achieve higher energy density, more heat will be generated and accumulated, thereby causing thermal runaway.
The Chinese patent application No. CN200880127749 discloses a battery pack with a heat-transfer medium introduced into the sealed pack. The technical solution of this invention is: the heat-transfer medium, with a boiling point less than 80° C., is introduced into the space between the battery cells, and the interior of the battery case is the vacuum state. However, the best working condition and proper heat-transfer medium are not disclosed. Actually, although using the same heat-transfer medium, the heat transfer efficiencies are dramatically different under different vacuum conditions. The shape and the structure of the pack case directly influence the heat dissipation effect, and may not be able to meet the heat dissipation requirement.
Therefore to address the above inefficiency, it is desirous to have a battery pack injected with a phase change material.